Treatment of gases and liquids

ABSTRACT

Gases or liquids are steam desulphided in the presence of a catalyst containing a uranium oxide together with a thorium oxide and/or a cobalt oxide. Air may also be present. The process is useful for desulphiding inorganic gases, for example effluent gases and for desulphiding organic compounds such as oils.

United States Patent [191, Nicklin et al.

[ 4} TREATMENT or GASES ANDVLIQUIDS [75] Inventors: Thomas Nicklin, Middleton;

Frederick Farrington, Sale, both of England [73] Assignee: The Gas Council, London, England [22] Filed: July 27, 19 72 [21] Appl. No: 275,697

Related U.S. Application Data [62] Division of Ser. No. 843,832, July 22, 1969, Pat. No.

[52] U.S. Cl 208/208 R, 208/213, 208/243 51 Int. Cl C10g 27/00,C10g 23/02 [58] Field of Search.....,....; 208/216, 213, 209, 208/208 R, 243

[S6] 7 References Cited UNITED STATES PATENTS 3,475,328 10/1969 Nicklin et a1. 208/243 Jan.8, 1974 Nicklin et a1, 208/243 Bertolacini et a1. 208/216 Primary ExaminerDelbert E. Gantz Assistant Examiner-G. J. Crasanakis Attorney.lames H. Marsh, Jr.

[57] ABSTRACT 10 Claims, N0 Drawings 1 TREATMENT OF GASES AND LIQUIDS This is a division of copending application Ser. No. 843,832, filed July 22, 1969, which issued as US. Pat. No. 3,714,328. I

The invention relates to the removal of sulphur containing compounds from gases or liquids.

In a number of processes in the gas, chemical and petroleum industries, it is desirable that the sulphur content of liquid or gaseous feedstocks employed in the process should be reduced to a low level. Furthermore, legislation in a number of countries, notably the United States of America, prohibits the discharge of effluent gases into the atmosphere unless the sulphur content of such gases is below a very low maximum concentration. 7 According to the present invention, there is provided a process for the treatment of gases or liquids to re move therefrom sulphur Containing compounds which process comprises contacting a mixture of steam and the gases or liquids to be treated with a catalyst comprising an oxide of uranium together with an oxide of thorium and/or an oxide of cobalt, whereby the sulphur present in said sulphur containing compound is converted into hydrogen sulphide. The hydrogen sulphide produced in the reaction may be collected and removed by methods known in the arts, such as by washing the gases with an aqueous solution of sodium vanadate and the sodium salt of anthraquinone disulphonic acid as described and claimed in British Pat. Specification No. 948270. Alternatively the hydrogen sulphide may be removed by contacting the gases withzinc oxide.

The active catalytic components are preferably disposed on the surface of a catalyst carrier, such as a-alumina or y-alumina. Other carriers which may be employed are silica, kaolin, powdered brick and alkali earth metal oxides such as the oxides of magnesium, calcium, strontium, barium, or mixtures thereof. The carrier may be in the form of spheres.

Where it is required to have a high counter-current flow of liquid and vapour phases, whilst at the same time maintaining a large solid surface area wetted by the liquid, and efficient mixing of the phases, the catalyst support can be shaped in the form of rings, or hollow cylinders, or saddles such as have been found effective in distillation practice. The size of rings used is preferably of the order of 17 mm outside diameter with a hole diameter of 10 mm.

Generally the uranium oxide, which may be in the form of U U 0 or other uranium oxides such as U0 would bepresent in an amount of from 1% to 80% by weight based on the total weight of the catalyst. Preferably the uranium oxide content is from 5% to 20%, and in certain cases it may be even more preferred to use a catalyst having a uranium oxide content of from 5% to by weight.

If present in the catalyst, thorium oxide, e.g. Th0, may be in an amount from 3% to 20% by weight, more preferably at least 8% or 10% by weight and not greater than by weight, based on the total weight of the catalyst.

If cobalt oxide is present in the catalyst, it is preferably present in an amount of from 10% to 15% by weight based on the total weight of the catalyst.

The catalyst may be prepared by any suitable process, for example by'the thermal decomposition of precursors for the metallic oxides forming the active components of the catalyst. Thus the catalyst may be formed by the thermal decomposition of the nitrates, or carboxylates, e.g. acetates, of the active metal components of the catalyst. Other precursors which may be used include thorium and cobalt uranates or diuranates.lf the catalyst includes a catalyst carrier, the surface of the carrier may be impregnated with the precursors of the metallic oxides constituting the active components of the catalyst, either from a melt or from a solution. The active metallic oxides can then be formed by heating the metal impregnated carrier either before use, or in situ under the conditions of the desulphiding process.

For example, in one method of forming a catalyst composition of the present invention, a refractory support, e.g. a-alumina is dipped in a bath containing a melt of the nitrates of uranium and of thorium and/or of cobalt. The coated support is subsequently calcined at 550 C to decompose the nitrates. The dipping operation may be repeated if necessary.

The process of the invention may be used for removing organic sulphur compounds and/or carbon oxysulphide or carbon disulphide from inorganic gases or gas mixtures, i.e. gases or gas mixtures containing no appreciable amounts of hydrocarbon. In such a process, the active components of the catalyst may consist essentially of uranium oxide and thorium oxide, and the process may be conveniently conducted at an elevated temperature of from 275 C to 500 C, or, preferably, from 420 C to 480 C. The reaction may be carried out at any desired pressure, such as atmospheric pressure or pressures as high as 25 or even 50 atmospheres. The process may therefore be used to remove sulphur containing compounds from inorganic gas streams which are to be further processed, and in which sulphur compounds are undesirable. In a particular application of the invention carbon oxysulphicle is removed from mix tures of carbon dioxide and carbonmonoxide. The process of the invention may also be used to purify exhaust gases from various processes, such'as those from rubber vulcanising, artificial fibres production, and tar distillation. The process of the invention may also be used to purify air in atmospheres polluted with the treatable sulphur compounds.

Another use of the process of the present invention is in the removal of sulphur compounds from organic compounds such as oils especially compounds normally in the liquid phase. The process may be conducted with compounds in either the gaseous or the liquid phase. The conditions must be such, however, that the steam does not condense. The ability to use liquid organic compounds is particularly useful in cases where decomposition is likely to take place before the boiling point is reached. In the case of organic feed-stocks, air may be added to the mixture of steam and compounds to be treated. The process is preferably to be conducted at a temperature of from 380 C to 460 C. The precise temperature used will depend on the circumstances of the reaction including the nature of the product to be treated, the proportions of steam and sulphur present and the space velocity of the reactant through the reaction zone.

There are several ways in which the process of themvention may be conducted. In one embodiment, the compound or compounds to be treated are introduced into a reactor vessel containing a bed of the catalyst, whilst steam, optionally together with air, is passed through the reactor. The compound or compounds to be treated may be in the vapour phase, i.e. as gas, or in the liquid phase. They may be introduced to the reactor together with the steam or mixture of steam and air, and pass up or down the reactor and through the catalyst bed. Alternatively the compound may be introduced separately from the steam or steam and air mixture, and may pass in counter-current thereto. From one part of the reactor may be extracted the fraction of the organic compound or compounds in the vapour, i.e. gaseous, phase. Any liquid fraction present may be extracted at another part of the reactor.

The hydrogen sulphide and steam and, if present, air will generally be present in the gas taken from the reactor.

If there is a liquid fraction drawn off from the reactor, the liquid will generally be extracted in the form of a foam containing steam and hydrogen sulphide. The fraction will be found to have been desulphided, but probably to a lesser extent than the gas fraction.

It is to be understood that the invention further comprises a gas or liquid, or an organic compound or mixture of compounds whenever purified by the process of the invention.

In order that the invention may be more fully understood the processes of the invention are illustrated by the following examples.

"EXAMPLE 1 cc of catalyst in the form of inch diameter spheres and comprising 9.1% Uranium and 11.4% C0- balt on oz-alumina support was placed in a silica tube and heated to 450 C. A test feedstock comprising a mixture of dioctyl sulphide and desulphided naphtha (1% dioctyl sulphide by volume) was passed through the tube at a rate of 22 cc/hour with slightly excess steam.

The product was washed with cadmium acetate solution and subsequently condensed. The amount of cadmium sulphide was determined iodometrically and the percentage conversion to hydrogen sulphide calculated. The conversion was found to be 77%.

EXAMPLE 2 1000 of catalyst comprising Uranium and 14.6. Thorium on /8 inch diameter alpha alumina spheres was placed in the silica tube and heated to 450 A feed stock similar to that used in Example 1 was passed through the tube and the resultant product washed with cadmium acetate before condensation. The amount of cadmium sulphate present was determined and the percentage conversion to hydrogen sulphide calculated as before.

The conversion was found to be 100%.

EXAMPLE l0 millilitres of catalyst in the form of Va inch diameter spheres and comprising 11.7% Uranium and 9.1%

- Thoria on alpha alumina support was placed in a silica tube and heated to 450 C. A test feedstock comprising a mixture of 0.7% dioctyl sulphide and 0.7% thionaphalene in primary flash distillate was passed through the tube at a rate of 20 millilitres/hour together with a mixed stream of air and steam at a temperature of 380 C. The water/steam flow rate was 20 millilitres/hour and the air flow rate was 0.1 cubic feet/hour.

The product was washed with cadmium acetate solution and subsequently condensed. The amount of cadmium sulphide was determined iodometrically and the percentage conversion to hydrogen sulphide calculated. The conversion was found to be 98% 99%.

EXAMPLE 4 This example is concerned with the removal of COS from a gas consisting essentially of 60% by volume CO- and 40% by volume CO. The COS content of this feed gas was 300 grains/100 ft. The CO /CO mixture containing the COS was admixed with about three times the minimum amount of steam which was required to convert the sulphur in the COS to H 5. The gas to be treated under steam was then passed through an externally heated tube containing the catalyst. The catalyst was supported on corundum and contained 8.9% by weight of uranium oxide and 10.5% by weight of thorium oxide. After the gas to be treated had been passed through the catalyst, it was cooled and treated with an absorber for H 8.

In order to determine the amount of COS in the treated gas, it was admixed with hydrogen and passed over a Nimox catalyst at 400 C. The H S thus produced was measured by Drager tubes.

The experiment described above was carried out at atmospheric pressure. I

The results obtained from carrying out the above procedure are as follows:

TABLE Test Space velocity Catalyst COS inlet H,S No. hour temp. 0C grll00 ft outlct p.p.m.

1 claim:

1. In a process for purifying a hydrocarbon stream which contains sulfur contamination comprising one or more of organic sulfur compounds, carbon oxysulfide and carbon disulfide, the steps of:

admixing steam with said sulfur contaminated hydrocarbon stream to produce an admixture thereof;

contacting said admixture at a temperature of from 275 C to 500 C with a catalyst consisting essentially of, as active ingredients, from 1 to percent by weight of an oxide of uranium and from 3 to 20 percent by weight of an oxide of thorium, all weight percentages being based on the total weight of the catalyst, whereby to convert the sulfur in said sulfur contamination into hydrogen sulfide; and thereafter removing said hydrogen sulfide from said admixture.

2. A process as set forth in claim 1 wherein said oxide of uranium is uranoso-uranic oxide.

3. A process as set forth in claim 1 wherein said oxide of uranium is uranium trioxide.

4. A process as set forth in claim 1 wherein the metallic oxides constituting the active ingredients of the catalyst are disposed on the surface of a catalyst carrier.

5. A process as set forth in claim 1 wherein air is added to said admixture.

6. A process as set forth in claim 1 wherein said hydrocarbon stream is maintained in gaseous form during said contacting step.

of uranium is present in said catalyst in an amount of from about 5 to 20 percent by weight of the latter.

10. A process as set forth in claim 1 wherein said oxide of uranium is present in said catalyst in an amount of from about 5 to 10 percent by weight of the latter. 

2. A process as set forth in claim 1 wherein said oxide of uranium is uranoso-uranic oxide.
 3. A process as set forth in claim 1 wherein said oxide of uranium is uranium trioxide.
 4. A process as set forth in claim 1 wherein the metallic oxides constituting the active ingredients of the catalyst are disposed on the surface of a catalyst carrier.
 5. A process as set forth in claim 1 wherein air is added to said admixture.
 6. A process as set forth in claim 1 wherein said hydrocarbon stream is maintained in gaseous form during said contacting step.
 7. A process as set forth in claim 1 wherein said oxide of uranium is present in said catalyst in an amount of from about 5 to 20 percent by weight of the latter.
 8. A process as set forth in claim 1 wherein said oxide of thorium is present in said catalyst in an amount of from about 8 to 15 percent by weight of the latter.
 9. A process as set forth in claim 8 wherein said oxide of uranium is present in said catalyst in an amount of from about 5 to 20 percent by weight of the latter.
 10. A process as set forth in claim 1 wherein said oxide of uranium is present in said catalyst in an amount of from about 5 to 10 percent by weight of the latter. 